Automatic or robotic pool cleaners having one or more electric motors contained in a housing are connected through a drive train that includes at least one drive wheel mounted on a rotating axle and an endless traction belt or drive track in the form of a loop that contacts the bottom and other surfaces of the pool to move the pool cleaner. The drive traction belt can serve as the primary means for moving the pool cleaner and is at all times in contact with the flat bottom and side walls of the pool, as well as any angular surfaces, such as steps, projecting curbs, and the transverse line that exists at the bottom between the deep and shallower ends of some pools. In cleaners of this design, the drive tracks are mounted inboard on either side and may be partially enclosed by the side walls of the housing.
Other pool cleaners known in the art employ cylindrical transverse brushes, generally constructed from foamed plastic material, mounted for rotation at either end of the housing, and the rotating brushes and provide the primary drive means for moving the cleaner across the flat surfaces to be cleaned. In these devices, endless drive tracks are provided as an ancillary means for propelling the cleaner up steps and across other transverse angular surfaces which would otherwise contact the base plate or housing of the cleaner between the rotating brushes. During normal operation on flat surfaces, the diameter or height of the brushes on devices of this design maintain the moving drive tracks a half-inch or more above the flat pool surface.
In the case of swimming pool cleaners of the prior art, the dimensions of the belt typically range from an inch to an inch and one-half wide, about one-eighth inch thick. The exterior surface of the belt is textured or provided with closely-spaced projecting elements intended to improve traction.
The drive tracks are generally fabricated by molding a synthetic or semi-synthetic flexible polymer compound that resists the effects of the sun and chemicals used to treat the water in the pool or tanks being cleaned. The drive track is mounted to pass around one or more pulley-like drive wheels and one or more tensioned idler wheels that engage the belt and retain it in position for rotational movement.
One problem that has been associated with pool cleaners of the prior art that climb and traverse the vertical side walls of the pool is their inability to advance past an inside corner, projecting ladder or other such object. As a result, these prior art cleaners will remain idling in a fixed position in a corner of the pool or at a ladder, wasting cleaning time and energy, awaiting a preprogrammed reversal of the drive tracks. If the pool is constructed with two or more ladders on opposite sides of the pool, the cleaner can be effectively "trapped" in one section of the pool, and must be manually moved to the other side of the ladders in order to complete its cleaning path.
It has also been found that the drive tracks of the prior art are not effective in moving the cleaner up steps or other raised surfaces of in-ground pools and this inability is a deficiency.
In addition, it has been found that the molded plastic cover of prior art pool cleaners can come into contact with the side wall of the pool, or both the side wall and bottom of the pool, as the cleaner moves along the bottom of the pool. This scraping action can also occur in concrete or gunnite pools having a large radius of curvature between the bottom and side walls. This repeated scraping of the surface of the housing detracts from its appearance, and over time, weakens the housing and can wear a hole through a corner or other projecting surface. The housing is a relatively expensive component of the cleaner and its replacement requires a substantially complete disassembly of the unit.
Another problem can develop in pools constructed with a vinyl or other flexible lining, it there the constant contact of the rigid plastic housing of the pool cleaner can eventually lead to damage to the liner, abrading, scratching and even tearing of the liner can occur at positions where the pool cleaner makes repeated contacts over time during its routine transit of the bottom and side wall surfaces.
In order to reduce or eliminate the aesthetic and physical damage to the housing, some manufacturers have installed projecting bumpers on the ends of the housing. In addition to increasing the cost and number of components requiring manufacture, assembly and inventory, these projecting bumper elements can interfere with the programmed movement of the cleaner, or can become trapped behind a ladder and altogether stop the movement of the cleaner.
It has also been found that some pool cleaners of the prior art can become disabled tipped over on their sides, so that neither the moving brushes nor drive tracks are in contact with a surface which might otherwise serve to provide traction for the device and enable it to right itself.
It is therefore one object of the invention to provide an improved construction for a self-propelled submersible pool cleaner that will prevent the housing of the cleaner from scraping the side walls and/or bottom of the pool.
It is also an object of the invention to provide an improved drive track that will facilitate the climbing of steps and over other angular projections.
It is another object of the invention to provide such an improved construction that is inexpensive and that does not required the assembly of additional components to the cleaner housing.
Another object of the invention is to provide means that will prevent a pool cleaner from being disabled or rendered inoperable by being turned on its side.
Yet another object of the invention is to provide a means of preventing further damage to the housings of existing pool cleaners by retrofitting these existing cleaners with an improved, but functionally compatible replacement element.
Another object of the invention is to prevent damage to the cleaner and/or to the pool liner resulting from impact when the cleaner travels down the wall on a diagonal path in impacts the bottom of the pool.